1. Field of the Invention
The present invention relates to a robot controller for controlling motions of a robot.
2. Description of the Related Art
Recently, humanoid robots, particularly walking of humanoid robots, are attracting attentions of the researchers. Most of the studies relating to walking of the humanoid robots use the ZMP (Zero Moment Point) criteria. The ZMP criteria include a control to retain the ZMP within a support polygon. Specifically, this approach includes modeling the humanoid robot and the environment around the robot, and solving a differential equation. However, accurate modeling becomes difficult if there are unknowns. Furthermore, a real time control becomes difficult because time is taken in solving the differential equation.
One approach is to use a method that does not employ the ZMP criteria at all. There have been known techniques, for example, that make use of a cyclic movement of a movable section of a robot, and adjust a phase of the cyclic movement so as to stabilize posture of the robot (See Japanese Patent Laid-Open Publication No. 2005-96068). The movable section can be a leg or an arm of a robot.
However, humanoid robots can performs different types of movements one after another. In this case, the cycle of the movable section varies depending on the type of movement performed by the robot. In other words, the movable section does not perform a cyclic movement when the humanoid robot performs different types of movements one after another. Because the movable section does not necessarily perform a cyclic movement, it becomes difficult in the conventional technique to control a posture of the robot.
There is a need to develop a technique enabling efficient control for stabilizing various motions of a humanoid robot without modeling the humanoid robot and the environment around the robot.